Manta rays munching on micro-plastics

More than a million tons of plastic are thought to enter Indonesia’s oceans every year.

Much of it is in the form of micro-plastics, and that could be harming iconic oceanic filter feeders such as the manta ray.

Murdoch University researcher Ellie Germanov is working to assess the impact of the plastics on manta rays and explore ways to reduce plastic waste, with Dr Gede Hendrawan and his Universitas Udayana team (Ayudian Swarry, Bintang Gustavina, Rai Ayu Saraswati and Surya Risuana).

She’s tracking the levels of micro-plastics (pieces with a diameter of less than five millimetres) in the feeding grounds of manta rays and whale sharks around the coastline of Nusa Penida and Komodo National Park in Indonesia, as well as fisheries in the Philippines, with plans for future research in the West Australian Coral Bay reefs.

Ellie hopes to use the information on plastics in feeding grounds and potentially in the guts of these animals to determine the effect microplastic may be having on reproduction and the success of the populations overall. The work is supported by the Marine Megafauna Foundation and the Ocean Park Conservation Foundation.

“Micro-plastics absorb toxins from the environment and concentrate them in much higher levels than in the surrounding waters—once these toxic plastics are ingested by filter feeders such as manta rays and whale sharks, toxins can build-up in the animals’ bodies,” Ellie says.

The team, along with recycling advocate Kennedy Diaz, have been interviewing more than 120 stakeholders and business owners to get an understanding of local attitudes towards management of plastic waste. Ellie says reducing waste is clearly a priority in the communities.

“While the waters of Southeast Asia are some of the worst affected in terms of plastic waste, plastics are still entering Australian waters—for example via plastic beads in facial scrubs and toothpastes, which are too small to be filtered during water treatment,” Ellie says.